An on-demand inkjet recording system ejects ink drops from a nozzle in accordance with an image signal, and forms an image on the recording paper with the ink drops. The on-demand inkjet recording system includes those of a heating element type and a piezoelectric element type.
In the heating element type system, a heating element in ink flow paths generates air bubbles in ink. The ink drops pushed by the air bubbles are ejected from a nozzle. On the other hand, in the piezoelectric element, a piezoelectric element being an actuator deforms, and the pressure of ink stored in ink cells is thereby changed. As a result, the pressurized ink drops are ejected from the nozzle.
An example of the piezoelectric element inkjet head includes nozzles and driving elements (actuators) corresponding to each other one to one. The actuators each include a piezoelectric element, and a common electrode and an individual electrode that apply voltage to the piezoelectric element. The common electrode and the individual electrode are each electrically connected to a driving circuit via a conductor pattern. When drive voltage is applied to the piezoelectric element from the driving circuit via the common electrode and the individual electrode, the piezoelectric element deforms. As a result, the ink supplied to the pressure cell is pressurized. Part of the pressurized ink forms ink drops, and the ink drops are ejected from a nozzle.
In an inkjet head including many driving elements (actuators), if the inkjet has a structure including the common electrode described above, a connection terminal that connects the common electrode and an external terminal for applying voltage is arranged only at the end of the head body. In such a structure, the maximum distance between the connection terminal of the common electrode and the driving elements increases as the size of the head body increases. For that reason, the voltage is changed due to wiring resistance, and it may affect driving of each driving element.
In addition, if the difference between the maximum distance and the minimum distance between the connection terminal of the common electrode and the driving elements is large, the difference between voltage changes in the driving elements is large and the stability of the driving of each driving element may be reduced. Further, in the case where the connection terminal of the common electrode is arranged only at the end of the head body, current concentration occurs, and thus a problem such as short-circuiting and wiring damage may occur.